Contact weld breaking means



Sept. 1, 1964 J. H. LEONARD CONTACT WELD BREAKING MEANS 3 Sheets-Sheet 1 Filed Dec. 23, 1960 0 R. mwz -58 m my? 4 w M A P A v EM 5 8 r 95 I 4 0 AAA? \K I-wIIIII,

Sept. 1, 1964 Y J. H. LEONARD 3,147,353

CONTACT WELD BREAKING MEANS Filed Dec. 25, 1960 5 Sheets-Sheet 2 BY 0; ream/r4 51.52,; z/as 1215:!

A Train! 9r P 1, 1964 J. H. LEONARD CONTACT WELD BREAKING MEANS 3 Sheets-Sheet 2:

Filed Dec. 23, 1960 BY as 7704 544e, 545: 'brefakw United States Patent 3,147,353 CONTACT WELD BAKING MEANS James H. Leonard, Clifton Heights, Pa., assiguor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a'corporation of Pennsylvania Filed Dec. 23, 1960, Ser. No. 77,976 Claims. (Cl. 200-416) The instant invention relates to circuit breaker mechanisms housed within narrow molded casings and more particularly to novel means for the breaking of welds formed at the cooperating contacts.

In recent years it has been the practice to construct circuit breakers for home and light industrial applications with casings whose Widths are one inch or multiples thereof. More recently, the trend has been to supply individual circuit breaker protection to many circuits even those carrying light loads. Because of this, the capacity of existing panelboards, while suflicient electrically, were not sufiicient in physical size to accommodate the greater numbers of circuit breakers. Further, panelboards having the requisite physical size to accommodate the greater number of circuit breakers were wasteful of material and space.

Thus, it became necessary to construct circuit breakers having narrow housings. For example, a typical circuit breaker of 20 amp rating was usually provided with a molded casing having a one inch width. A circuit breaker of this rating can be replaced by a circuit breaker whose molded insulating housing is one-half inch in width.

In the circuit breaker of this type described in the J. H. Leonard copending application Serial Number 11,768, filed February 29, 1960, entitled Circuit Breaker Having Bimetal Rigidly Secured to Cradle, and assigned to the assignee of the instant invention, a latch means is provided which is comprised of main and intermediate latch members with the intermediate latch member having one portion thereof utilized as a latch surface for magnetic tripping and another portion utilized as a latch surface for the thermal tripping, The bimetal, or thermal tripping element, is positioned to deflect out of the plane of movement of the releasable cradle to which the bimetal is affixed while the latch members are arranged to pivot around axes perpendicular to the releasable cradle.

Until automatic tripping has actually occurred the relationship between the bimetal and intermediate latch member is unaffected by the position of the main latch member which is movable directly through the action of the magnetic tripping device. Similarly, a deflection of the bimetal will in no way effect the relationship between the elements comprising the magnetic trip means.

The absolute independence of the thermal and magnetic trip device results in the advantage of being able to adjust the trip characteristics of the breaker so as to achieve low magnetic tripping without utilizing a coil. Further, the thermal tripping characteristic may be calibrated prior to installing the thermal trip unit into the circuit breaker case. The latter is accomplished by providing a sub-assembly comprising a releasable cradle, the bimetal having one end rigidly secured to the cradle and the intermediate latch member pivoted to the cradle and operatively positioned so as to cooperate with the free end of the bimetal to form the latch for the thermal tripping means. I

In the circuit breaker described in the aforesaid copending application 11,768, it was found that it was not unusual for welds to form between the cooperating contacts. Often the strength of the main operating spring was not great enough to break these welds either during manual or automatic tripping.

In order to overcome this difiiculty during manual operation, the contact arm is provided with an offset positioned in the path of movement of the operating handle extension so as to be engaged thereby during manual opening. Thus, the manual opening force is applied di rectly to the contact arm to break any welds between the cooperating contacts.

In the case of automatic tripping it has been found that in prior art constructions at the instant the cradle is releasedthe main operating spring furnishes a mere shear force acting to separate the cooperating contacts. This shear force often is not of sufficient magnitude for breaking of the contact welds.

In order to overcome this diiiiculty, the instant invention provides a novel configuration for the contact arm and cradle in the conducting joint region. Thi construction is such that the component of force is produced which acts upon the contact arm in such a direction that a bending moment is produced of sufiicient magnitude for breaking of contact welds.

This construction includes a reentrant offset portion to the cradle notch which receives the contact arm. The contact arm in turn is provided with a portion of reduced size which is normally disposed within the reentrant notch portion. When the cradle is released the contact arm moves out of the reentrant notch portion and engages a surface of the cradle which is appropriately shaped and positioned so that the main spring exerts a component of force which is efiective to produce a bending moment for the breaking of contact welds.

Thus, a primary object of this invention is to provide a novel construction for a narrow molded case circuit breaker which is economical to construct, is reliable in operation, and is simple to calibrate.

Another object is to provide a circuit breaker of this type having novel means for the breaking of contact welds.

Still another object is to provide a circuit breaker of this type having a novel construction in the conducting joint region between the contact arm and cradle, whereby the main spring is effective to exert a force acting in a direction to produce a bending moment tending to produce relative motion between the cooperating contacts rather than exerting a mere shear force for contact separation.

These as well as other objects of this invention shall become readily apparent after reading the following description of the accompanying drawings in which:

FIGURES 13 .are side elevations of a circuit breaker constructed in accordance with the teachings of the instant invention, with the cover of the casing removed to reveal the operating mechanism. In FIGURE 1 the circuit breaker is in the On position, in FIGURE 2 the circuit breaker is in the manual Oil position, and in FIG- URE 3 the circuit breaker is in the Tripped position.

FIGURE 1A is a fragmentary cross-section of the circuit breaker housing taken through line 1A-1A of FIGURE 1 looking in the direction of arrows 1A1A.

FIGURE 4 is an exploded perspective of the circuit breaker operating mechanism.

FIGURE is a side elevation of the cradle sub-assembly.

FIGURES 5A and 5B are cross-sections taken through lines 5A5A and 5B--5B, respectively, of FIGURE 5, looking in the direction of the respective arrows.

FIGURE 6 is an end view of the contact arm.

FIGURE 7 is a fragmentary side elevation of the cradle in the region of the joint between the contact arm and the cradle.

FIGURES 8 and 9 are fragmentary side elevations showing the relationship between the contact arm and cradle in the joint region. arm is in normal operating position, while in FIGURE 9 the contact arm has been moved to the position it occupies relative to the cradle when contact welds are present during automatic tripping.

Now referring to the figures, circuit breaker 20 includes a housing comprised of a case 21 and cover 22 mated to each other along line 23 and secured by rivets 23a. The current path through circuit breaker 20 comprises line terminal 24, conducting strap 25, stationary contact 26, movable contact 27, contact arm 28, the pressure joint 29 at the upper end of contact 28, releasable cradle 30, bimetal 31, conducting braid 32, load terminal member 33, and load terminal 79.

Adapter means 77, of a type fully described in the J. H. Leonard copending application Serial No. 18,411, filed March 29, 1960, entitled Panelboard Adapter, and assigned to the assignee of the instant invention is utilized to electrically connect line terminal 24 to a panelboard bus bar (not shown).

Circuit breaker 20 includes an operating member 34 having an extension 35 which extends upwardly through an opening 36 in the top of housing 21, 22 to provide a manual operating handle. Operating member 34 is also provided with an arcuate portion 37 extending in the direction of movement of handle 35 and disposed within arc groove 38 of case 21 and a similar groove in cover 22. The upper end of handle arm 39 extends into suitable recesses of operating member 34 while the lower end of arm 39 abuts against a rounded internal formation of case 21 to form a pivot 40 for operating member 34.

Main operating spring 41 is secured at one end thereof 42 to arm 39 where the upper end thereof engages member 34 while the other end 43 of spring 41 is connected to movable contact arm 28. Spring 41 is a tension spring comprised of an open loop with elongated arms extending in opposite directions. The tension force exerted by spring 41 urges the upper end of contact arm 28 to abutv cradle 30 at joint 29.

With sub-assembly 180 (FIGURE 5) in the latched position of FIGURES 1' and 2, circuit breaker 20 may be operated manually between the On and Off positions. When handle 35 is moved to the right with respect to FIGURE 1 at such time as the spring end at 42 passes to the right of a line joining spring end 43 and joint 29, the line of action of spring 41 will be so positioned as to affect a snap opening of contacts 26, 27 by pivoting contact arm 28 in a counterclockwise direction about joint 29 to the Off position of FIGURE 2. The reverse action takes place as handle 35 is moved to the left with respect to FIGURE 2. During this operation, at such time as the line of action of spring 41 extending between spring ends 42, 43 passes to the left of the line joining spring end 43 and joint 29 in FIGURE 2, contact arm 28 will be snapped in a clockwise direction about joint 29 to the closed position of FIGURE 1.

Sub-assembly 100 (FIGURE 5) comprises cradle 39 which is a generally V-shaped member having an opening 44 near the apex thereof which receives a case embossment 45 serving as a pivot for sub-assembly 100. Bimetal 31, which forms a part of sub-assembly 100, is fixedly secured at one end 46 thereof as by welding to In FIGURE 8 the contact cradle leg 47 in the region of aperture 44. Sub-assembly 100 further comprises intermediate latch member 48 pivotally mounted at pin 49 to the offset portion 30a at the free end of cradle leg 40. In forming portion 30a stop formation 71 is also formed. Stop 71 cooperates with the notch 72 in latch member 48 to limit movement of latch member 48 about its pivot pin 49. Pin 49 is constructed of insulating material as is sheet 70 which is interposed between latch member 48 and cradle offset portion 38a. Thus, latch member 48 is insulated from cradle 30.

Pin 49 and latch member 48 are secured to cradle 30 by element which is constructed of a good electrically conductive spring material. Element 90 is an elongated member having a U-shaped portion 91 at one end and at the other end an offset portion 92 with an open ended slot 93.

The arm 94 of U-shaped portion. 91, which is not directly connected to the main portion 95 of element 90, confronts one surface of main portion 95 while portion 92 is offset beyond the other surface of main portion 95. The web of U-shaped portion 91 is disposed within cradle notch 96 with the upper end of contact arm 28 being positioned between the arms of the U-shaped portion 91 which encompass the region of joint 29 to provide guidance for arm 28 as it moves between the positions of FIGURES 1-3. The arms of U-shaped portion 91 are slightly spread as a result of engagement with embossments 97A, 973 (FIGURE 6) extending from opposite surfaces of contact arm for a purpose to be hereinafter explained.

The portion of element 90 defining slot 93 is received by annular groove 98 in the body of pivot pin 49 to retain pin 49 mounted to cradle 30. As slot 93 is mated to pin 49 the main portion 95 snaps over cradle projection 88 to retain element 99 mounted to cradle 30. Thus, it is seen that elements 30, 48, 49, 70 and 90 are readily assembled without the necessity of utilizing special deforming tools or assembly jigs.

Offset portion 30a must be bent from its free position in order for slot 93 to receive the reduced portion of pm 49. In so being bent, the main portion 95 is firmly seated against cradle 30 and intermediate latch-48 is biased axially along pin 49 toward cradle offset portion 30a. This assures a uniform latch bite for successive resettings after thermal tripping. The rounded portion 99 at the end of pin 49 opposite its enlarged head 89 serves to align sub-assembly 100 with respect to the internal walls of housing 21, 22.

Since contact arm 28 abuts cradle 30 at joint 29 to the right of embossment 45, the force exerted by main operating spring 41 acts to rotate sub-assembly 100 counterclockwise about pivot 45. However, sub-assembly 108 is restrained against movement in a counterclockwise direction through the engagement of intermediate latch member 48 with main latch member 51. Main latch member 51 is comprised of spring material and in cludes a portion of reduced area which extends over the back of magnet 52 so as to form a pivot at 53 for armature 54 which is secured to main latch member 51 by welding.

Magnet 52 is of generally U-shaped cross-section with U to form the energizing tum therefor. The biasing action of the spring material forming main latch member 51 urges armature 54 in a clockwise direction about its pivot 53 away from magnet 52. The lower end of armature 54 abuts a case formation 56 to establish the an gap between armature 54 and magnet 52 and also establishes the latching position for member 51. Magnetrc tripping takes place when a predetermined magnitude of current flows through terminal member 33 causing magnet 52 to generate flux which attracts armature 54 counterclockwise about pivot 53. This moves main latch member 51 with respect to FIGURE 1 so that sub-assembly 100 is no longer restrained. Thus, subassembly 100 under the influence of main operating spring 41 rotates in a counterclockwise direction about pivot 45. When pivot 29 moves to the left of the line of action of spring 41 in its position of FIGURE 1, spring 41 will urge contact arm 28 in a counterclockwise direction about pivot 29 to bring about a snap opening of contacts 26, 27.

The circuit breaker elements are now in the tripped position of FIGURE 3 with sub-assembly 180 being positioned by the abutment of case embossment 55 and cradle surface 55a while one side of contact arm offset 75 abuts cover formation 76. Offset 75 extends at right angles to the plane of movement of contact arm 28 and movable contact 27 is mounted to the other side of offset 75.

After magnetic tripping, resetting is accomplished by moving operating handle 35 to the extreme right position from the intermediate tripped position of FIGURE 3. During this movement handle arm extension 68 engages cradle 30 along surface 61 so that sub-assembly 180 is moved clockwise against the force of spring 41 to the latched position of FIGURE 2. As latch member 48 moves past latch member 51 the rounded portion 63 of intermediate latch member 48 cams latch 51 to the right until latch surface 64 passes below the lower end of main latch member 51.

Time delay tripping is accomplished by a deflection of the free end of bimetal 31 out of the plane of movement of cradle 30. When this deflection is suflicient to free bimetal offset tip 31a from intermediate latch 48 the action of tension spring 41 will rotate cradle 38 in a counterclockwise direction about pivot 45. Initially intermediate latch member 48 is retained by main latch member 51 so that there is relative movement between cradle 30 and intermediate latch member 48 about pivot 49. As the distance between pivot 49 and main latch member 51 increases, a point is reached where intermediate latch member 48 is free of main latch member 51 and the sub-assembly 108 moves freely to the tripped position of FIGURE 3. It is to be noted that bimetal tip 31a presents a rolled surface for engagement by latch member 48 so that ,shear forces are materially reduced and.

successive trip operations are more uniform.

I Resetting after thermal tripping is accomplished by moving handle 35 from the intermediate trip position of FIGURE 3 to the extreme right position of FIG- URE 2.- At the latter portion of this movement intermediate latch member 48 engages case embossment 65 which forces intermediate latch member 48 in a counterclockwise direction about its pivot 49 to a point where member 48 is free of the edge of bimetal extension 31a and at this time the free end of bimetal 31 moves toward the plane of movement of cradle 30 into latching position.

It is to be noted that as the latch bite between bimetal offset 31a and member 48 changes due to a deflection of bimetal 31 the latch bite between surface 64 and member 51 is not affected. Similarly, a change in the magnetic latch bite 64, 51in no way affects the thermal latch bite 31a, 48. Thus, the thermal and magnetic trips are operated independently of one another.

I Cover 22 is mated with case 21 to form housing'chamber 80, wherein the operating mechanism is disposed, also forms vent opening 81 (FIGURE 6) which extends for distance X (FIGURE 1) along the bottom of housing 21, 22. Vent 81 is greatly elongated, being very narrow in width, say .020". It is to be noted thatthe cover surface 82 forming vent 81 extends toward vent 81 initially experiencing turbulence within chamber 81 since vent 81 is so narrow. After the gases are substantially deionized the upper portion. of surface 82 not confronted by surface 83 acts to direct the deionized gases through vent 81 out of housing 21, 22.

During movement of contact arm 28 the upper end thereof often loses direct contact with cradle 30 at pressure joint 29. If there were no parallel conducting paths, arcing would occur at joint 29 which would soon become pitted and thereafter present a high resistance connection. The instant invention provides these parallel conducting paths in the form of spring element whose body portion is self biased against cradle leg 58 and whose U-shaped portion arms are self biased into engagement with contact arm 28 at embossments 97A, 97B. The engagement between element 90 and embossments 97A, 97B is maintained even though contact arm 28 moves a considerable distance away from joint 29.

' Embossments 97A, 97B are formed as spherical segments to reduce the frictional forces between spring element 98 and contact arm 28 which must be overcome in moving contact arm relative to cradle 30.

In circuit breakers of the type hereinbefore described it is not unusual for the contacts 26, 27 to weld with spring 41 not being of sufficient strength to break these welds. For manual breaking of contact welds handle extension 39 is pivoting clockwise, as handle 35 is moved to the right from its position of FIGURE 1, and engages offset 101 which is depressed from the plane of contact arm 28 (FIGURE 4).- Thus, the manual opening force is applied directly to contact arm 28 for breaking of contact welds.

The breaking of contact welds during automatic tripping is facilitated by the unique shapes of cradle 30 and contact arm 28 at the region of joint 29. This is best explained by reference to FIGURES 7-9.

The legs 47, 58 of cradle 38 are arranged to form notch 102 which receives contact arm 28. Notch 182 is of generally V-shape, as indicated by the dotted line in FIGURE 7, and is provided at its apex region with an offset re entrant portion 103. The upper end of contact arm 28, at the upper end thereof, is provided with a section of reduced width having a rounded portion 184 which is normally entered into reentrant, or first, portion 103 of notch 182 as in FIGURE 8. It is to be noted that rounded portion 104 appears to be comprised of an are greater than a semi-circle.

During automatic tripping, cradle 30 is unlatched. At this time, its counter clockwise motion about center 45 is relatively unrestrained. Assuming a contact weld, the main spring 41 acting on contact arm 28 acts to move rounded portion 184 out of reentrant notch portion 103, to the position of FIGURE 9, whereat rounded portion 104 engages a second portion of the notch 102.

. Notch surface 185 is so shaped that the relocation of rounded portion 104 thereat serves to exert both a shear force and a bending moment on this weld. Both types of forces are present to act on the weld because:

(1) Vertical translation of contact arm 28 is unrestrained since this would produce a counter clockwise motion of cradle 30 and the cradle 30 is not restrained against a counter clockwise motion.

- (2) Rotation of contact arm 28 counter clockwise about the weld, i.e. bending of the Weld, is relatively unrestrained since the shape of the cradle notch is such that counter clockwise rotation of contact arm 28 Will also produce counter clockwise rotation of cradle 30, which is unrestrained against motion in this direction.

The bending moment created by the force of spring 41 acting on contact arm 28 acts on the weld greatly increasing the stress at the Weld, ultimately breaking the weld.

Thus, this invention provides novel means for contact weld breaking during both manual and automatic operating of a narrow molded case circuit breaker.

Although there has been described preferred embodiments of this invention, many Variations and modifications will not be evident to those skilled in the art and, therefore, the scope of this invention is to be limited not by the specific disclosure herein detailed, but only by the appended claims.

I claim:

l. A circuit breaker comprising a pair of cooperating contacts and an operating mechanism for operating said contacts into and out of engagement; said mechanism including a releasable cradle, latch means for restraining said cradle in a reset position, an operating spring urging said cradle to a tripped position, and a manually operable member for operating said contacts into and out of engagement; said mechanism further including a tripping means having a portion operatively positioned for engagement with said latch means and when deflected sufliciently to disengage said latch means permitting said spring to move said cradle to its said trip position wherein. said contacts are disengaged; a movable contact arm carrying at one end thereof one of said cooperating contacts and having the other end biased into abutment with said cradle at a first region constructed to provide a pivotal support for said contact arm; said other end and said first region being constructed for cooperation with one another whereby upon movement of said cradle to its said trip position forces are exerted upon said contact arm directed in a direction creating a bending moment which separates said contacts breaking welds which may exist therebetween; said first region comprising a notch including first and second spaced notch portions; said other end having a portion normally disposed within said first notch portion when said first contacts are engaged; the movement of said cradle towards its said trip position, with said contacts being welded, moving at least a part of said contact arm portion from said first notch portion to said second notch portion; the relocation of said contact arm portion in said second notch portion dimensionally related to the location of said welded contacts, and the movement of said cradle member, to generate a force component along said contact arm in a direction aiding in breaking the welded relationship of said contacts.

2. A circuit breaker comprising a pair of cooperating contacts and an operating mechanism for operating said contacts into and out of engagement; said mechanism including a releasable cradle, latch means for restraining said cradle in a reset position, an operating spring urging said cradle to a tripped position, and a manually operable member for operating said contacts into and out of engagement; said mechanism further including a tripping means having a portion operatively positioned for engagement with said latch means and when deflected sufficiently to disengage said latch means permitting said spring to move said cradle to its said trip position wherein said contacts are disengaged; a movable contact arm carrying at one end thereof one of said cooperating contacts and having the other end biased into abutment with said cradle at a first region constructed to provide a pivotal support for said contact arm; said other end and said first region being constructed for cooperation with one another whereby upon movement of said cradle to its said trip position forces are exerted upon said contact arm directed in a direction creating a bending moment which separates said contacts breaking welds which may exist therebetween; said first region comprising a notch including an offset reentrant portion; said contact arm other end having a portion biased to a position where it is normally disposed Within said reentrant portion and as said cradle commences movement toward its said trip position at least a part of said contact arm portion normally disposed in said reentrant portion is moved out of said reentrant portion.

3. The circuit breaker as set forth in claim 2 in which said contact arm portion is generally rounded and is comprised of an are apparently more than a semi-circle.

4. The circuit breaker as set forth in claim 2 in which the notch is generally V-shaped with the reentrant portion disposed at the apex region of the V.

5. The circuit breaker as set forth in claim 4 in which the contact arm is somewhat L-shaped with the arm having the other end being disposed in said generally V-shaped notch.

6. The circuit breaker as set forth in claim 5 in which said contact arm portion is generally rounded and is comprised of an are apparently more than a semi-circle.

7. A circuit breaker comprising a pair of cooperating contacts and an operating mechanism for operating said contacts into and out of. engagement; said mechanism including a releasable cradle, latch means for restraining said cradle in a reset position, an operating spring urging said cradle to a tripped position, and a manually operable member for operating said contacts into and out of engagement; said mechanism further including a trip-. ping means having a portion operatively positioned for engagement with said latch means and when deflected sufiiciently to disengage said latch means permitting said spring to move said cradle to its said trip position wherein said contacts are disengaged; a movable contact arm carrying at one end thereof one of said cooperating contacts and having the other end biased into abutment with said cradle at a first region constructed to provide a pivotal support for said contact arm; said other end and said first region being constructed for cooperation with one another whereby upon movement of said cradle to its said trip position forces are exerted upon said contact arm directed in a direction creating a bending moment which separates said contacts breaking welds which may exist therebetween; said first region comprising a notch including first and second spaced notch portions;

said other end having a portion normally disposed within said first notch portion when said first contacts are engaged; the movement of said cradle towards its said trip position, with said contacts being welded, moving at least a part of said contact arm portion from said first notch portion to said second notch portion; the relocation of said contact arm portion in said second notch portion dimensionally related to the location of said welded contacts, and the movement of said cradle member, to generate a force component along said contact arm in a direction aiding in breaking the welded relationship of said contacts; said other end being biased into abutment with said cradle by said operating spring.

8. The circuit breaker as set forth in claim 7 in which 7 the operating spring is a tensioned member connected to said contact arm; a manually operable means connected to said spring for changing the relative position of said spring and said contact arm to bring about snap opening and closing of said contacts.

9. The circuit breaker as set forth in claim 7 in which the manually operable means includes a portion engageable with a portion of said contact arm only during manual opening of said contacts to apply a manual opening force directly to said contacts.

10. A circuit breaker comprising a pair of cooperating contacts and an operating mechanism for operating said contacts into and outof engagement; said mechanism including a releasable cradle, latch means for restraining said cradle in a reset position, an operating spring urging said cradle to a tripped position, and a manually operable member foroperating said contacts into and out of engagement; said mechanism further including a tripping means having a portion operatively positioned for engagement with said latch means and when deflected sufficiently to disengage said latch means permitting said spring to move said cradle to its said trip position wherein said contacts are disengaged; a movable contact arm carrying at one end thereof one of said cooperating contacts and having the other end biased into abutment with said cradle at a first region constructed to provide a pivotal support for said contact arm; said first region comprising a notch including an offset reentrant portion; said contact arm other end having a portion biased to a position where it is normally disposed within said reentrant portion and as said cradle commences movement toward its said trip position at least a part of said contact arm portion normally disposed in said reentrant portion is moved out of said reentrant portion; said notch being partially defined by a surface adjacent to said reentrant portion; said surface being engaged by said contact arm other end as it moves out of said reentrant portion; said. surface being operatively positioned to direct a component of force produced by the operating spring against said contact arm whereby as said contact arm other end leaves said reentrant portion and a bending moment is created which separates said 10 2,902,560

contacts breaking Welds which may exist therebetween.

UNITED STATES PATENTS Johnson Oct. 25, 1938 Wise Apr. 19, 1949 Thomas Feb. 3, 1953 Cole Sept. 22, 1953 Drobney et a1. Nov. 2, 1954 Stanback et a1 Sept. 1, 1959 

1. A CIRCUIT BREAKER COMPRISING A PAIR OF COOPERATING CONTACTS AND AN OPERATING MECHANISM FOR OPERATING SAID CONTACTS INTO AND OUT OF ENGAGEMENT; SAID MECHANISM INCLUDING A RELEASABLE CRADLE, LATCH MEANS FOR RESTRAINING SAID CRADLE IN A RESET POSITION, AN OPERATING SPRING URGING SAID CRADLE TO A TRIPPED POSITION, AND A MANUALLY OPERABLE MEMBER FOR OPERATING SAID CONTACTS INTO AND OUT OF ENGAGEMENT; SAID MECHANISM FURTHER INCLUDING A TRIPPING MEANS HAVING A PORTION OPERATIVELY POSITIONED FOR ENGAGEMENT WITH SAID LATCH MEANS AND WHEN DEFLECTED SUFFICIENTLY TO DISENGAGE SAID LATCH MEANS PERMITTING SAID SPRING TO MOVE SAID CRADLE TO ITS SAID TRIP POSITION WHEREIN SAID CONTACTS ARE DISENGAGED; A MOVABLE CONTACT ARM CARRYING AT ONE END THEREOF ONE OF SAID COOPERATING CONTACTS AND HAVING THE OTHER END BIASED INTO ABUTMENT WITH SAID CRADLE AT A FIRST REGION CONSTRUCTED TO PROVIDE A PIVOTAL SUPPORT FOR SAID CONTACT ARM; SAID OTHER END AND SAID FIRST REGION BEING CONSTRUCTED FOR COOPERATION WITH ONE ANOTHER WHEREBY UPON MOVEMENT OF SAID CRADLE TO ITS SAID TRIP POSITION FORCES ARE EXERTED UPON SAID CONTACT ARM DIRECTED IN A DIRECTION CREATING A BENDING MOMENT WHICH 